def bin_search(ok, ng, is_ok):
   while abs(ok-ng) > 1:
      mid = (ok+ng)//2
      if is_ok(mid):
         ok = mid
      else:
         ng = mid
   return ok
def solve(N, X, C):
   INF = float("INF")
   def is_good(range_, C):
      start, stop = range_
      for c in C:
         m = start + ((1<<c) - start) % (1<<(c+1))
         if (start>>c)&1 == 0 and stop <= m:
            return False
      return True
   S = set(C)
   pos = X
   tovisit = []
   while True:
      found = []
      for c in S:
         if pos&(1<<c):
            found.append(c)
      if found:
         for c in found:
            S.remove(c)
         tovisit.append((pos, found[:]))
      if not S:
         break
      cands = []
      for c in S:
         npos = pos + ((1<<c) - pos) % (1<<(c+1))
         cands.append(npos)
      pos = min(cands)
   tovisit.insert(0, (X, []))
   used = []
   cands = []
   for pos, found in tovisit:
      used += found
      D = list(set(C) - set(used))
      lo = bin_search(X - 2**60 - 10, X+1, lambda l: is_good((l, X), D))
      if lo < 0: lo = -INF
      cands.append((pos - lo) * 2)
   ans = min(cands)
   return ans
T = int(input())
for _ in range(T):
   N, X = map(int, input().split())
   C = list(map(int, input().split()))
   ans = solve(N, X, C)
   print(ans)